A central valve of this type is part of a pivot motor actuator system which includes a rotor which is adjustable through a hydraulic pressure at one of its two operating connections respectively in one of its two rotating directions.
It is an ongoing development goal for pivot motor actuation systems on the one hand side to have a minimum load on a hydraulic pump since this hydraulic pump typically has to supply all consumers in a vehicle. Another development goal is quick adjustability. In order to better comply with these contradicting requirements it is known to use pressure peaks during cam shaft adjustment through check valves.
In the pivot motor actuation system that is known from DE 10 2006 012 775 A1 pressure chambers of the rotor are provided with check valves so that pressure spikes that occur during quick adjustment are being utilized. Thus, a portion of the hydraulic fluid from the pressure cavities associated with one rotating direction is supplied to a flow from the oil pump so that a greater volume flow is provided for the other pressure cavities.
It is known from EP 2 375 014 A1 to integrate check valves into the central valve in order to use cam shaft adjustment torques in that band check valves are arranged at an inside of a housing tube. At both operating connections and at the supply connection of the housing tube a respective band check valve presses from an inside against the housing tube. When sufficient pressure is supplied to the respective connection the band check valve opens so that hydraulic fluid flowing into the central valve at one operating connection can be supplied to the other operating connection together with hydraulic fluid from the supply connection. Starting from a central position of the central valve initially a switching position is proportionally controllable in which pressure spikes of the operating connection to be unloaded are blocked relative to the operating connection to be loaded. Thereafter another switching position is controllable in order to use the cam shaft adjustment torques.
From DE 10 2010 061 337 A1 a valve for a pivot motor actuator is known in which each operating connection A or B is divided into an operating connection A* or B* for using cam adjustment torques and an operating connection A or B for directly passing hydraulic fluid to the pressure cavities of the torque motor actuator. The operating connections A* and B* for using cam adjustment torques include check valves. In a center position of the piston both operating connections A* and B* are blocked through a common annular bar. The blocking of the annular bar in the center position improves control quality in the center position.
EP 1 596 039 B1 relates to a valve for using cam adjustment torques, thus check valves are provided in annular bars of a hollow piston. The adjustment is provided exclusively through cam adjustment torques. A tank drain connection is not provided.